Disclosed herein is a printed stretch sensor that can be prepared by printing methods such as ink jet printing.
Stretch sensors typically come in a one-dimensional form (only stretching across a single axis). By weaving or knitting stretch sensors into a fabric, multiple degrees of freedom can be achieved. Stretch-sensitive material can also be glued onto an elastic surface, but these techniques are labor-intensive and result in limited range of motion. By creating printed stretch sensors on an elastic surface, one can achieve high range of motion, and manufacture is as simple as printing a material onto a surface.
Conductive elastomers are used in applications requiring deformability and electrical conductivity, such as for gaskets used in EMI-shielding. One notable feature of conductive elastomers is that they change conductivity as they are stretched. By measuring the electrical resistance through such a material, one can calculate the degree of stretch.
Conductive stretchable inks are known, as disclosed in, for example, “Inkjet-Printed Stretchable Silver Electrode on Wave Structured Elastomeric Substrate,” Seungjun Chung, Jaemyon Lee, Hyunsoo Song, Sangwoo Kim, Jaewook Jeong, and Yongtaek Hong, Applied Physics Letters, 98, 153110 (2011) and Copending application Ser. No. 13/182,579, filed Jul. 14, 2011, entitled “Stretchable Ink Composition,” with the named inventors Yiliang Wu, Qi Zhang, Ke Zhou, Yu Qi, and Nan-Xing Hu, the disclosures of each of which are totally incorporated herein by reference.
Much of the work related to conductive elastomers has attempted to overcome the challenge of conductivity loss during deformation. In contrast, the articles disclosed herein take advantage of this property.
Accordingly, while known articles and compositions are suitable for their intended purposes, a stretch sensor which stretches in two dimension (i.e., along two axes) that can be prepared by printing a conductive ink in an imagewise pattern onto a deformable nonconductive substrate in such a way that both materials can stretch and return back to their original shape is desirable.